There are a variety of approaches for forming particles from flowable masses. Often the flowable mass is a melt. Melts are commonly prepared by providing one or more raw materials in a molten form into a batch mixer. The mixer is sized and dimensioned to provide for a desired residence time for the raw material or materials in the mixer to sufficiently mix and or react the raw material or materials and provide a uniform temperature to the melt. After exiting the batch mixer, the melt can optionally be passed through one or more filters to remove deleterious matter. The melt is then fed into a feed pump that moves the melt via a feed pipe from the feed pump to the apparatus that dispenses the melt to form particles.
The melt can leave the batch mixer at a particular temperature. Depending on how the batch mixer is operated, it can be challenging to maintain and or establish the desired temperature of the melt within the batch mixer. In transit, heat conduction through the wall of the feed pipe can result in cooling of the melt. To counter such heat loss and to raise the temperature of the melt to the desired temperature, heat can be applied to the feed pipe. If the melt in the feed pipe is at a particular temperature and heat is applied to the feed pipe from outside the feed pipe the temperature of the boundary layer and melt flowing proximal the boundary layer may be raised more than the change in temperature of the melt at the centerline of the feed pipe. At the outlet of the feed pipe to the dispensing apparatus, the temperature profile of the melt can be non uniform, with relatively cooler melt along the centerline and relatively warmer melt near the wall of the feed pipe. This tends to result in the melt having different temperatures at different locations within the dispensing apparatus. The energy required to provide heat increases production costs. Further, providing for uniform temperature across and along the feed pipe can be challenging, particularly if the initial conditions are non-uniform across the cross section of the feed pipe.
It is known to be challenging to form particles having a uniform shape from melts having non-uniform temperatures. Part of the challenge is that once the melt is dispensed to form the particle, the melt is still flowable and may not maintain its originally dispensed shape. The consequence of the melt having a non-uniform temperature across the dispensing apparatus is that the particles formed can have a non-uniform shape across the dispensing apparatus.
Depending on the application in which the particles will be used, particles having a uniform shape can be more or less desirable. For instance, if the particles are used in an application in which the particles are dissolved in a solvent, having a uniform dissolution time can be desirable. Further, the uniformity of the particles can be perceived by those who use the particles as a secondary indicia of quality of the particles comprising a product. For instance, in a consumer product comprising particles, consumers are thought to perceive non-uniform particles within a single package or across multiple packages as an indication that little care or control was maintained in designing and producing the product.
With these limitations in mind, there is a continuing unaddressed need for an apparatus and method for forming particles that provides for uniformly shaped particles.